Known fuel systems commonly include a fuel pump having one or more cam driven plungers arranged to pressurise fuel within a pumping chamber for delivery to the injectors of the associated engine. In a unit pump/injector scheme, a single plunger is driven to pressurise fuel within a pumping chamber, from where high pressure fuel is delivered to the delivery chamber of an injector located within a housing common to the pump elements. Alternatively, the pump and the injector may communicate through a separate high pressure fuel line interconnecting the pumping chamber with an injector delivery chamber.
It is a recent development in diesel engine technology to provide the engine with an after treatment device for the purpose of improving exhaust emission levels. For regeneration purposes, such devices periodically require an injection of fuel to the engine sometime after a main injection event (referred to as “late post injection”). Typically, such late post injection of fuel may be required several times for any one tank of fuel used.
It is an object of the present invention to provide a fuel system which enables this to be achieved.